Screw or helical compressors are commonly used in air conditioning applications to compress refrigerant as part of the refrigeration cycle. Screw compressors are composed of meshing screw or helical rotors. While two rotor configurations are the most common design, screw compressors are also known in the art having three, or more, rotors housed in respective overlapping bores so as to co-act in pairs. The rotors of a typical screw compressor are mounted in bearings at each end in housing end plates at the inlet and discharge side. Refrigerant is compressed by the screw rotors toward the discharge side and discharged through ports and into a discharge line.
In normal applications, oil becomes entrained in the refrigerant as a result of the need to lubricate the screw compressor bearings and rotors while the refrigerant passes through and is compressed, and accordingly, needs to be removed after discharge before progressing through the rest of the refrigeration or air conditioning cycle. Accordingly, the combined oil and refrigerant mixture is carried through the compression cycle and then discharged into an oil separator where the oil is removed from the refrigerant. From the oil separator, the refrigerant flows to the condenser.
Oil separators are generally of two types, vertical or horizontal. Horizontal oil separators are usually cylindrical with an inlet at one end. In a horizontal separator, the combined oil and refrigerant mix enters through the inlet. The mixture is directed against the inner surfaces of the separator so that the oil droplets impinge on the surfaces and collect there. Under the influence of the flow and gravity, the oil tends to collect at a particular portion near the bottom of the separator where it is removed through a drain. Optionally, mesh separators or baffles may be used to increase the impingement surface on which oil collects. The refrigerant then exits from the upper portion of the separator above the oil collection area.